MozStumbler

brew install gradle
gradle build
gradle installRelease

Signing

In order to sign the APK, you will want to create a 'gradle.properties' file. The content should look like the following except it should contain your key signing information:

StoreFile=<path to file>
StorePassword=<password>
KeyAlias=<key alias>
KeyPassword=<password>.

To generate a key, search the internet for details. This command is probably what you want:

keytool -genkey -v -keystore my-release-key.keystore -alias mozstumbler -keyalg RSA -keysize 2048 -validity 10000

To verify the apk has been signed, you can run this command:

jarsigner -verify -verbose -certs build/apk/MozStumbler*